Version C: Instructions
Midterm is worth 46 points, not including extra credit, which gives you up to 13 extra points.
RIGHT NOW- fill in your ID number, the bubbles and your version letter on the answer sheet, do
this now so you don’t forget.
There are four versions of the exam. The questions are designed to look similar yet give you the
wrong answer if yo ucopy. If you copy, you are most likely copying the wrong answer, this
makes cheating even more pointless than normal, please don’t do it.
If you think someone nearby may be copying, or something is simply disturbing you, please let
me know and we can adjust people’s seats appropriately. Tell me as early as possible.
Be sure to sign the sign in sheet. This is my record that you attended the class. If you are not
sitting in your assigned seat for a reason approved by me, you’ll need to make sure to write the
seat where you are actually sitting next to your name.
You will also need to show your ID to the TA when you turn in your exam.
Only the answer sheet will be graded. You may (and should) keep the exam sheet. Go
home, retake it, see how you did . If you write any work on scrap paper, the question sheet or
anywhere other than the space given, it will not be graded and you will not get any credit for it.
Do not write on the back of the sheets, do not write anything you want graded anywhere other
than the space given. I’d suggest writing in pencil or doing scratch work elsewhere and then
copying over.
Use your time wisely. Do problems you know first, do problems worth many points first.
Exams will be sent through eee dropbox. They will be graded the same day as you take it, and
the grades will be posted at least by the next morning, if not sooner. It will take a week or more
to get the exams back to you depending on how backed up the system is. I can’t make this go
faster, it is completely out of my hands.
Finally, relax. At that point there is nothing that being stressed will do for you. So take a
deep breath, pick up your writing utensil and show me how amazing you are at
chemistry!
Long Answer Problems- Partial Credit Allotted, please show your work on the
answer sheet to receive partial credit.
Problem 1- When calcium carbonate is added to hydrochloric acid, calcium chloride, carbon dioxide and
water are produced. The balanced reaction below shows this.
32.0 g of calcium carbonate are combined with 10.0 g of hydrochloric acid. Please find the limiting
reagent the amount of moles of calcium chloride present.
HCl is the limiting reagent. 0.137mol CaCl2 is present
Problem 2- An unknown compound contains C, H and O. 4.20 g of a substance is combusted and
produced 10.3 g CO2 and 4.20 g H2O. Find the moles of C, H, O present in the initial sample and then find
the empirical formula of the compound.
10.3g CO2(1mol CO2 /44.009g CO2)= 0.234mol C (12.011g/mol C)=2.81g C
=0.234mol C / 0.0575=4
4.20 g H2O (2mol H/18.0148g H2O)=0.465 mol H (1.01g/mol H)=0.470 g H
=0.465 mol H /0.0575=8
4.20g-(2.81+0.470)g=0.92g O (1mol/15.999g)=0.0575 mol O
= 0.0575 mol O /0.0575=1
Answer: 0.234 mol C, 0.465 mol H, 0.0575 mol O empirical formula C4H8O
Problem 3- In the spectrum of atomic hydrogen a violet line is observed at 434 nm. This is part of the
balmer series and therefore has a final energy level of n=2. Determine the energy of the photon, the E
and the initial energy level of the electron during the emission of the energy that leads to this spectral
line.
Energy of photon=4.57x10-19J
E= -4.57x10-19J
Ni=5
(partial credit was given here if you forgot to make the delta E negative and therefore got 1.47, however
you HAD to explain that you knew that 1.47 couldn’t be the correct answer, and so obviously there was
something else wrong that you couldn’t figure out, if you put 1.47 down for an energy level calculation
there is no way we could give you partial credit since it must be an integer. )
Problem 4- Explain the difference between a wavefunction and a probability density. Give the symbol for each
in your explanation and also state what sign (positive or negative) each is allowed to be. Identify which graph is the
wavefunction and which is the probability density for the particle in a box.
Problem 5- Draw the energy level diagram for hydrogen and nitrogen. Including 1s, 2s and 2p orbitals.
(Be sure to label all orbitals and the way Energy increases). How does hydrogen’s diagram differ from
other atoms (hint: not just in the number of electrons)? Which orbital is the most penetrating (in
either)? In nitrogen which orbital is the most shielded?
Bonus Question: Points allotted based on how good your answer is (hint: unless you are pretty sure of
this one skip and come back at the end)
Give examples of light emission events seen in life. How do these vary from each other?
Short Answer Problems- No partial credit allotted, be sure to round to proper significant
figures, include all units and check for calculation mistakes. All answer must be on the line in the answer
sheet. No work will be graded. Please do all work on scrap paper in the back of this packet. Put only
your answer on the sheet. See Answers Below
1) Give the chemical formula from Ferrous Sulfate:
2) Give the chemical name from MnCl2:
3) Give the chemical formula for phosphorous pentoxide
4) Give the name for H3PO4:
5) Calculate the frequency of an electron ejected from the surface of a copper sheet that has a work
function of 7.53 × 10-19 J if the electron has a KE of 1.3*10-19 J
6) What is the effect of increasing the intensity of a laser of a frequency less than the threshold
frequency?
7) What is the effect of increasing the intensity of a laser of a frequency greater the threshold
frequency?
8) Determine the wavelength of a protein of 5.3156x10-23kg/molecule moving at 1.5 m/s
9) Calculate the minimum uncertainty in position of a nitrogen atom moving 1.5*103 m/s that has
uncertainty of 5% of that value.
10) Give the electron configuration for Nitrogen:
11) Give the electron configuration for Ag:
12) Give the electron configuration for Ag+:
13) Provide the correct order of increasing atomic radius for the following: C, N, F
14) Provide the correct order of increasing electron affinity for : K, Ca, Br
15) Provide the correct order of increasing ionization energy of Carbon, Nitrogen and Oxygen
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16) What are the possible values of and ml if n=4.
17) How many orbitals are allowed for the situation in number 16? How many electrons are allowed?
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18) What values of is/are associated with the d subshell?